Everyone has external batteries that juice their phones and tablets -- but what about their laptop? Until recently, it was challenging to find a compatible power bank, with each brand having one or more proprietary power plugs. So, if you bought a battery that didn't come with the right connector, you could be out of luck.

However, now that a number of laptops use USB Type-C for charging, it's easier to get a portable charger that just works. One of the best laptop power banks we've tested, Anker's $79.99 PowerCore Speed 20,000 PD, is lightweight, affordable and provides hours of extra power to any laptop that charges over Type-C.

Design

At 0.79 pounds and 6.6 x 2.4 x 0.9 inches, the PowerCore Speed 20,000 PD is thin and light enough to fit into a laptop bag, without weighing you down or taking space away from your other gadgets. It even slid into my front jeans pocket, though it was a tight fit. Omnicharge's $209 Omni 20 USB-C battery weighs a much heftier 1.1 pounds, while the $150 Razer Power Bank, tips the scales at 0.74 pounds.

The curved, rectangular black plastic chassis doesn't really stand out in a crowd, but it looks professional and inoffensive. A set of four blue lights on the top shows how much juice you have left (four lights is 100 percent). Pressing the power button on the right side turns on the battery and activates the status lights.

AC Adapter

The PowerCore comes with a very compact AC adapter that you use to charge the battery, but it also works effectively with any phone, tablet or laptop that supports USB Power Delivery and doesn't need more than 30 watts of juice. The power prongs fold in to make this wall-wart style plug even smaller.

So, even if you leave the battery at home, you can take the adapter and use it in lieu of the power brick that came with your laptop. However, most laptop power bricks deliver at least 45 watts of power, so it's possible that the PowerCore's adapter may not charge your system as quickly or deliver enough power to charge it at all. When we plugged the adapter into a Google Pixelbook, the notebook charged without a problem.

By contrast, neither the Omni 20 nor the Razer Power Bank comes with an AC adapter. Both require you to use the one that came with your laptop, or buy your own.

Ports

The PowerCore Speed 20,000 PD has just two ports: a Type-C port that supports USB Power Delivery, and a regular USB Type-A port that you can use to simultaneously charge a second device such as a phone or tablet while you juice your laptop.

However, if you're using the PowerCore to charge just one device at a time, we recommend powering it from the Type-C port, which supports rapid charging. We were able to get both a Samsung Galaxy S8 and a Motorola Z2 Play to go into their quick-charging modes when we connected them to the battery's USB Type-C port, but not when we used the Type-A port.

However, competitors offer more ports. The Razer Power Bank has dual USB Type-A ports, along with a single Type-C connector. The Omni 20 has two USB Type-A ports and a pair of USB Type-C ports, and ,an also serve as a portable USB hub.

Performance

As its name implies, the Anker PowerCore Speed 20,000 PD holds 20,000 milliamp hours of electricity. That compares favorably to the Razer Power Bank's 13,800 mAh capacity and is about on par with the Omnicharge Omni 20's 20,100 mAh unit.

The PowerCore's 20,000 mAh is enough juice to charge a typical phone, such as a Samsung Galaxy S8 or an iPhone 8, as many as six times. Anker says that the PowerCore can also completely charge a 2016 MacBook (the 12-inch model, not the Pro). However, many laptops have higher capacity batteries than the MacBook, so those won't get a full charge from the PowerCore.

When we attached the PowerCore to a Lenovo Yoga 920, which itself has a 48 watt-hour battery, the laptop charged to 67 percent capacity in 2 hours and 27 minutes. We also used the laptop while it was charging. The Omni 20 was faster, charging the test laptop to 88 percent capacity in an hour and 29 minutes.

You can also use the PowerCore to run a laptop that has no juice left in its internal battery. When we ran our Laptop Mag Battery Test 2.0, which involves continuous surfing over Wi-Fi, with a discharged Yoga 920 connected to the battery, the Yoga clocked 7 hours and 54 minutes. That's about 77 percent of the 10 hours and 14 minutes that the Yoga 920 lasted when we tested it at 100 percent charge. WIth the Omni 20 battery attached, the test laptop endured for a nearly identical 7 hours and 42 minutes.

Using the included AC adapter, it took between 3 and 4 hours to charge the PowerCore to its full capacity. So, if you leave the battery plugged in overnight, it will be more than ready for you in the morning.

Compatibility

It's important to note that the PowerCore can deliver only 22.5 watts of power to a laptop, while the Omni 20 USB-C can send 60 watts and the Razer Power Bank 45 watts.

More powerful, USB Type-C laptops, such as the MacBook Pros or Dell's XPS 15, will definitely need one of these more powerful batteries. However, you pay a lot more for both of these options as the Omni 20 costs $209 and the Razer Power Bank rings up $149.

Bottom Line

The PowerCore Speed 20,000 PD offers the best balance between portability, price and capacity that we've seen on a laptop power bank. Users with laptops that require a higher wattage may want to consider a more expensive alternative like the Razer Power Bank or the Omnicharge Omni 20. However, if you need several more hours of endurance for your lightweight, USB Type-C-enabled laptop, the PowerCore is a great choice.